Preheat a grill or grill pan to medium high. Toss the onion, banana peppers and 1/3 cup of the pickle juice in a bowl. Whisk the hummus with 3 to 4 tablespoons water in another bowl until smooth and pourable.

Thinly slice the steak against the grain, then cut crosswise into bite-size pieces. Toss with the remaining 3 tablespoons pickle juice, 1 tablespoon olive oil, and salt and pepper to taste.

Brush the pitas on one side with the remaining 1 tablespoon olive oil and season with salt and pepper. Grill, oiled-side down, until lightly toasted, about 1 minute.

Remove the pitas from the grill and top with the steak. Drain the onion and peppers; divide evenly among the pitas. Top with the lettuce and drizzle with the hummus sauce. Top with hot sauce, if desired.